MC68HC12 Datasheet, PDF (180/478 Pages) Motorola, Inc – The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit

Clock Functions
Bit 7
6
5
0
0
SLDV5
RESET:
0
0
0
SLOW — Slow mode Divider Register
4
SLDV4
0
3
SLDV3
0
2
SLDV2
0
1
SLDV1
0
Bit 0
SLDV0
0
$003E
Read and write anytime.
A write to this register changes the SLWCLK frequency with minimum
delay (less than one SLWCLK cycle), thus allowing immediate tune-
up of the performance versus power consumption for the modules
using this clock. The frequency divide ratio is 2 times (SLOW), hence
the divide range is 2 to 126 (not on first pass products). When
SLOW = 0, the divider is bypassed. The generation of E, P and
M clocks further divides SLWCLK by 2. Hence, the final ratio of Bus
to EXTALi Frequency is programmable to 2, 4, 8, 12, 16, 20, ..., 252,
by steps of 4. SLWCLK is a 50% duty cycle signal.
Technical Data
180
Clock Functions
MC68HC912DT128A — Rev 4.0
MOTOROLA